A ferry is something very common in Malta. We took several times the ferry to get from Valletta to Sliema or the other way around (1.5 euro).
We also took a roundtrip to Gozo which was only 4.65 euro per person Gozo Channel Service We read in several places that you only have to buy your ticket upon your return, but seems it’s only valid for cars. Passengers by foot have to buy the return ticket in Cirkewwa. However, you don’t need your ticket to get on Gozo. You only need to scan the ticket to enter the terminal when heading back to Malta.
From Cirkewwa we visited Comino with Comino Ferries. Here you pay 13 euro per person for a retour ticket. They have a different schedule during summer and winter season. You can easily check it on their website.
A nice and efficient way to get back from the 3 cities to Valletta is by an old fashioned Maltese Gondola. You pay 2 euro per person and they drop you off near the elevator to the upper Barrakka Gardens. You can also take the Gondola in the opposite direction.
Recently there are also two companies who operate a fast ferry from Valletta to Gozo, but we didnt use it. They claim it takes less than 45 minutes. More info on their websites (Gozo fast ferry and Virtu Gozo)